System and method for wireless communication in a frequency division duplexing region

ABSTRACT

A method and system for using half-duplex base stations and half-duplex nodes in a Frequency Division Duplexing region to provide wireless connectivity between the half-duplex base stations and customers in multiple sectors of a cell. The method and system can use two physical channels to form two logical channels. Each logical channel shares both physical channels during alternating frames of time. The half-duplex nodes can include a millimeter-wave band frequency synthesizer configured to transmit and receive on different channels to and from the half-duplex base station. Re-use patterns of the physical channels are used for deployment of half-duplex base stations and half-duplex nodes in the FDD region to minimize co-channel interference and interference due to uncorrelated rain fade. Additional methods and systems utilize full-duplex base stations and smart antenna to communicate with the half-duplex nodes.

RELATED APPLICATIONS

This application claims priority to provisional application Ser. No.60/233,757, filed Sep. 14, 2000, titled “FIBERLESS-DEVELOPING A SHORTTERM FREQUENCY DIVISION DUPLEX SOLUTION” which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to wireless communication systems and to a methodand system for using such a system in a Frequency Division Duplexingregion.

2. Description of Related Art

A wireless communication system facilitates two-way communicationbetween a plurality of subscriber units (fixed and portable) and a fixednetwork infrastructure. Exemplary communication systems include mobilecellular telephone systems, personal communication systems (PCS), andcordless telephones. The key objective of these wireless communicationsystems is to provide communication channels on demand between theplurality of consumer subscriber units and their respective basestations in order to connect the subscriber unit user with the fixednetwork infrastructure.

Subscriber units typically communicate through a node with the basestation using a “duplexing” scheme thus allowing the exchange ofinformation in both directions of connection. Transmissions from thebase station to the nodes are commonly referred to as “downlink”transmissions. Transmissions from the nodes to the base station arecommonly referred to as “uplink” transmissions. In wireless systemshaving multiple access schemes a time “frame” is used as the basicinformation transmission unit.

Depending upon the design criteria of a given system, systems havetypically used either time division duplexing (TDD) or frequencydivision duplexing (FDD) methods to facilitate the exchange ofinformation between the base station and the nodes. In a TDDcommunication system, the base station and the nodes use the samechannel, however, their downlink and uplink transmissions alternate oneafter the other to prevent interference. In a FDD communication system,the base station and the nodes use different channels for their downlinkand uplink transmissions, respectively. Thus, the concern forinterference between uplink and downlink transmissions is mitigated in aFDD communication system as compared to a system using TDD. However, theincreased cost and complexity in deploying a FDD communication systemoften outweighs this obvious advantage over a TDD communication system.

In both TDD and FDD systems, each base station and node includes a modemconnected to an outdoor unit (“ODU”). The modem is configured tomodulate an outgoing signal and demodulate an incoming signal. If themodem is configured to modulate and demodulate simultaneously, the modemis a “full-duplex” modem. If the modem is not configured to modulate anddemodulate simultaneously, but rather switches between modulating anddemodulating, the modem is a “half-duplex” modem. Similarly, the ODU canbe configured as a full-duplex or half-duplex ODU. A full-duplex ODU isconfigured to transmit an outgoing signal and receive an incoming signalat the same time. A half-duplex ODU would alternate between transmittingand receiving.

In an exemplary FDD communication system, the modem and ODU operatesimultaneously to transmit and receive information. Since this occurssimultaneously, any subcomponents that might be common to the transmitand receive signal paths through the modem and ODU are not shared. Incontrast, since the modem and ODU in an exemplary TDD communicationsystem are half-duplex, components which may be common to the transmitand receive paths can be shared. Such sharing reduces the cost of thesystem.

As opposed to allowing each region to select an FDD or TDD communicationprotocol based on such advantages and disadvantages, certain specificregions are restricted by communication regulations. These communicationregulations often mandate the use of different channels, i.e. frequencybands, for uplink and downlink communications similar to an FDDcommunication system. For example, in Germany, a 26 GHz band is FDDoriented since the uplink channel and downlink channel are clearlydefined. In a typical case, a service provider is granted 2 or 4 channelpairs (2×28 MHz each) and is required to maintain a channel separationbetween the uplink and downlink channels.

By requiring a service provider to use different uplink and downlinkchannels, there is little incentive to use half-duplex modems or ODUs.If an exemplary halfduplex modem or ODU were used, a significant loss inbandwidth would be incurred.

Consequently, there is a need for a system and method that allows theuse of half-duplex modems and half-duplex ODUs in an FDD communicationsystem. Furthermore, this system and method should simplify the re-useof available channels and limit co-channel interference between multiplebase stations or multiple nodes in such a region.

SUMMARY OF THE INVENTION

The systems and methods of the present invention have several features,no single one of which is solely responsible for its desirableattributes. Without limiting the scope of this invention as expressed bythe claims which follow, its more prominent features will now bediscussed briefly.

One aspect of the invention relates to a method for communicatingbetween half-duplex nodes and a base station, where each half-duplexnode is configured to transmit on an uplink channel and receive on adownlink channel in a frequency division duplexing (“FDD”) manner. Themethod comprises transmitting modulated data from a base station to afirst half-duplex node during a first time frame on a first channel andtransmitting modulated data from a second half-duplex node to the basestation during the first time frame on a second channel. The methodfurther comprises transmitting modulated data from the base station tothe second half-duplex node during a second time frame on the firstchannel, wherein the first time frame precedes the second time frame,and transmitting modulated data from the first half-duplex node to thebase station during the second time frame on the second channel.

In another aspect of the invention, a wireless communication system isconfigured to transmit and receive over channels between half-duplexnodes and a base station in a frequency division duplexing (“FDD”)manner. The system comprises a first node comprising a first modem and afirst outdoor unit coupled to the first modem and configured toalternate between transmitting modulated data over a first channel andreceiving modulated data over a second channel and a second nodecomprising a second modem and a second outdoor unit coupled to thesecond modem and configured to alternate in transmitting modulated dataover the first channel and receiving modulated data over the secondchannel. The system further comprises a base station comprising a firsthalf-duplex base station modem configured to modulate and demodulatedata transmitted to and received from the first outdoor unit and a firsthalf-duplex base station outdoor unit coupled to the first half-duplexbase station modem and configured to transmit modulated data to thefirst outdoor unit over the second channel and receive modulated datafrom the first outdoor unit over the first channel. The system furthercomprises a second half-duplex base station modem configured to modulateand demodulate data transmitted to and received from the second outdoorunit and a second half-duplex base station outdoor unit coupled to thesecond half-duplex base station modem and configured to transmitmodulated data to the second outdoor unit over the second channel andreceive modulated data from the second outdoor unit over the firstchannel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a block diagram of a base station communicating with a firstnode and a second node in a Time Division Duplex (TDD) manner.

FIG. 1 b is a block diagram of a frame structure that includes twophysical channels for use with the communication system of FIG. 1 a.

FIG. 1 c is a block diagram of a base station communicating with a nodein a Frequency Division Duplex (FDD) manner.

FIG. 1 d is a block diagram of a frame structure that includes twophysical channels for use with the communication system of FIG. 1 c.

FIG. 1 e is a block diagram of a base station communicating with a firstnode and a second node in an FDD communication region.

FIG. 1 f is a block diagram of a frame structure that includes twophysical channels for use with the communication system of FIG. 1 e.

FIG. 1 g is a block diagram of a first node and a second nodecommunicating with a full-duplex base station in an FDD communicationregion.

FIG. 2 is a block diagram of a frame structure that includes twophysical channels for use with the communication system of FIG. 1 g.

FIG. 3 is a block diagram showing the signal paths through the first andsecond nodes.

FIG. 4 is a block diagram of nodes in a first sector and nodes in asecond sector communicating with a base station in an FDD communicationregion.

FIG. 5 is a block diagram of a frame structure that includes twophysical channels for use with the communication system of FIG. 4.

FIG. 6 illustrates an example of a downlink subframe for use by the basestation in transmitting information to the nodes in the first sector andto the nodes in the second sector on the downlink channel A of FIG. 5.

FIG. 7 illustrates an example of two uplink subframes for use by thenodes in the first sector and the nodes in the second sector intransmitting information to the base station.

FIG. 8 illustrates a sequence for transmitting an uplink subframe mapalong with attributes of the downlink subframe, both within the downlinksubframe.

FIG. 9 is a block diagram of a base station that includes a full-duplexRF module and two half-duplex IF modules.

FIG. 10 is a diagram showing uplink channels A and B being used fourtimes in a cell by half-duplex nodes.

FIG. 11 illustrates four adjacent sectors from four different cellswhere co-channel interference occurs due to uncorrelated rain fades.

FIG. 12 shows the sectors from FIG. 11 configured to use system widesynchronization to reduce the co-channel interference caused byuncorrelated rain fades.

The features, objectives, and other advantages will become more apparentfrom the detailed description set forth below when taken in conjunctionwith the drawings wherein like parts are identified with like referencenumerals throughout.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout this description, the embodiments and examples shown shouldbe considered as exemplars, rather than as limitations on the presentinvention.

FIG. 1 a is a block diagram of a base station 100 communicating with afirst node 208(a) and a second node 208(b) in a Time Division Duplexmanner. The system provides wireless connectivity between the basestation 100 and the first and second nodes 208(a), 208(b). The first andsecond nodes are positioned at fixed customer sites in a coverage area.The coverage area is served by base station 100. The coverage area canbe in the shape of, for example, a square containing multiple sectors.Node 208(a) and node 208(b) can be located in different sectors whilecommunicating with base station 100. The base station may serviceseveral hundred or more residential and business nodes (not shown).Users may include both residential and business customers.

Each node 208(a), 208(b) can include a half-duplex modem 106, ahalfduplex outdoor unit (“ODU”) 105, and an antenna 110, for example, adirectional antenna. The modem 106 is configured to modulate an outgoingsignal and demodulate an incoming signal. The ODU 105 is configured toupconvert the outgoing signal received from the modem 106 and downconvert the incoming signal received from the antenna 110. Each nodereceives its incoming signal and transmits its outgoing signal on thesame band of frequencies.

The upconversion and down conversion of the incoming and outgoingsignals can be performed in a plurality of stages. Each stage within theODU 105 shifts the signal from a higher to a lower frequency or from alower to a higher frequency. For example, the ODU in FIG. 1 a performseach upconversion and down conversion in two stages. To this end, theODU 105 includes a radio frequency (“RF”) module 210 and an intermediatefrequency (“IF”) module 212. The RF module 210 steps the incoming signaldown to an intermediate frequency at which point the IF module furthersteps the signal down to a base band signal. The base band signal isthen processed by the modem 106. For an outgoing signal that has beenmodulated by the modem 106, the IF module 212 steps the signal up fromthe base band frequency to an intermediate frequency. The IF module 212then steps up the outgoing signal to the radio frequency prior to thetransmission of the signal by the antenna 110. Alternatively, the upconversion and down conversion can be performed in a single stage or inmore than two stages.

The term “module,” as used herein, means, but is not limited to, asoftware or hardware component, such as a FPGA or ASIC, which performscertain tasks. A module may advantageously be configured to reside onthe addressable storage medium and configured to execute on one or moreprocessors. Thus, a module may include, by way of example, components,such as software components, object-oriented software components, classcomponents and task components, processes, functions, attributes,procedures, subroutines, segments of program code, drivers, firmware,microcode, circuitry, data, databases, data structures, tables, arrays,and variables. The functionality provided for in the components andmodules may be combined into fewer components and modules or furtherseparated into additional components and modules. Additionally, thecomponents and modules may advantageously be implemented to execute onone or more computers.

The base station 100 shown in FIG. 1 a includes two half-duplex modems106, two half-duplex ODU 105, and two antennas 110. The base station 100is configured to communicate with nodes in multiple sectors. Basestation components 206(a) communicate with node 208(a). While, basestation components 206(b) communicate with node 208(b). Similarly, node208(a) communicates with base station components 206(a). Node 208(b)communicates with base station components 206(b). Thus, the base station100 communicates with both nodes 208(a), 208(b). For ease ofdescription, only one node is shown communicating with each base stationmodem in FIG. 1 a. However, multiple nodes can be present in any givensector to form a point to multi-point communication system with the basestation. With multiple nodes, the antenna 110 in FIG. 1 a transmits andreceives between the nodes in one sector of a coverage area. A differentantenna 110 may transmit and receive between the nodes in another sectorof a coverage area or in the same sector but another physical channel.The base station modems 106, ODUs 105, and antenna 110 operate asdescribed with reference to nodes 208(a), 208(b).

FIG. 1 b is a block diagram of a frame structure that includes twophysical channels. The frame structure can be used with thecommunication system of FIG. 1 a. FIG. 1 b represents a discrete timesegment. Physical channel A 202 is allocated for downlinks and uplinksbetween the base station components 206(a) and the node 208(a) (See FIG.1 a). Physical channel B 204 is allocated for downlinks and uplinksbetween the base station components 206(b) and the node 208(b) (See FIG.1 a). Since physical channel A 202 includes the uplinks and downlinksbetween node 208(a) and base station components 206(a), physical channelA forms a logical channel between node 208(a) and base stationcomponents 206(a). Since physical channel B 204 includes the uplinks anddownlinks between node 208(b) and base station components 206(b),physical channel B forms a logical channel between node 208(b) and basestation components 206(b).

The base station components 206(a) downlink to node 208(a) during asubframe 116 of physical channel A 202. The node 208(a) uplinks to thebase station components 206(a) during subframe 118 of physical channel A202. Subframe 116 and subframe 118 together form a frame 112. The basestation components 206(b) downlink to node 208(b) during a subframe 120of physical channel B 204. The node 208(b) uplinks to the base stationcomponents 206(b) during subframe 122 of physical channel B 204.Subframe 120 and subframe 122 together also form a frame 112.

FIG. 1 c is a block diagram of a base station 406 communicating with anode 209 in a Frequency Division Duplex (FDD) manner. The base station406 includes a full-duplex modem 408, a full-duplex ODU 410, and afull-duplex antenna 412. The base station 406 is configured to transmitan outgoing signal and receive an incoming signal simultaneously ondifferent channels. The full-duplex modem 408 is configured to modulateand demodulate an incoming signal and to demodulate an outgoing signalsimultaneously. The full-duplex ODU down converts the incoming signalfrom a radio frequency in stages to a base band frequency. Thefull-duplex ODU also upconverts a modulated base band signal in stagesprior to transmission of the outgoing signal at the radio frequency.Alternatively, the up conversion and down conversion can occur in onestage or more than two stages.

The full-duplex ODU 410 can include a full-duplex intermediate frequency(“IF”) module 409 and a full-duplex radio frequency (“RF”) module 411.The full-duplex IF module 409 is configured to simultaneously upconvertan outgoing signal and down convert an incoming signal on differentchannels. The full-duplex RF module 411 is configured to simultaneouslyupconvert the outgoing signal from the IF module and down convert anincoming signal from the antenna 412. The antenna 412 is configured tosimultaneously transmit to and receive from a node 209. For ease ofdescription, only one node is shown in FIG. 1 c. However, multiple nodescan be present in any given sector to form a point to multi-pointcommunication system with the base station. With multiple nodes, theantenna 412 in FIG. 1 c transmits and receives between the nodes in onesector of a coverage area.

The node 209 shown in FIG. 1 c includes a full-duplex modem 408, afull-duplex ODU 410, and an antenna 412. The node communicates with basestation 406. The modem 408, ODU 410, and antenna 412 operate asdescribed with reference to base station 406.

FIG. 1 d is a block diagram of a frame structure that includes twophysical channels. The frame structure can be used with thecommunication system of FIG. 1 c. FIG. 1 d represents a discrete timesegment. Physical channel A 203 is allocated for downlinks from the basestation 406 to the node 209 (See FIG. 1 c). Physical channel B 205 isallocated for uplinks from node 209 to the base station 406 (See FIG. 1c). Since physical channel A 203 and physical channel B 205 togetherinclude the uplinks and downlinks between node 209 and base station 406,both channels together form a single logical channel between node 209and base station 406.

The base station 406 downlinks to node 209 during a subframe 216 ofphysical channel A 203. The node 209 uplinks to the base station 406during subframe 218 of physical channel B 205. Subframe 216 and subframe218 together form a frame 220.

FIG. 1 e is a block diagram of a base station 200 communicating with afirst node 402 and a second node 404 in an FDD communication region. Thesystem 300 provides wireless connectivity between the base station 200and the first and second nodes 402, 404. The first and second nodes 402,404 are positioned at fixed customer sites in a coverage area. Thecoverage area is served by base station 200. The coverage area can be inthe shape of, for example, a square containing multiple sectors. Node402 and node 404 can be located in different sectors while communicatingwith base station 200. The base station may service several hundred ormore residential and business nodes (not shown). Users may include bothresidential and business customers.

Each node 402, 404 can include a half-duplex modem 106, a half-duplexoutdoor unit (“ODU”) 108, and an antenna 110, for example a directionalantenna. The modem 106 is configured to modulate an outgoing signal anddemodulate an incoming signal. The ODU 108 is configured to upconvertthe outgoing signal received from the modem 106 and down converts theincoming signal received from the antenna 110. The ODU is furtherconfigured to shift the frequency of either the incoming or outgoingsignal to a different frequency. By shifting one of the signals, thenode transmits at a frequency that is different than the frequency atwhich the node receives an incoming signal.

The upconversion and down conversion of the incoming and outgoingsignals can be performed in a plurality of stages. Each stage within theODU 108 shifts the signal from a higher to a lower frequency or from alower to a higher frequency. For example, the ODU in FIG. 1 e performseach upconversion and down conversion in two stages. To this end, theODU 108 includes a radio frequency (“RF”) module 210 and an intermediatefrequency (“IF”) module 212. The RF module 210 steps the incoming signaldown to an intermediate frequency at which point the IF module furthersteps the signal down to a base band signal. The base band signal isthen processed by the modem 106. For an outgoing signal that has beenmodulated by the modem 106, the IF module 212 steps the signal up fromthe base band frequency to an intermediate frequency. The IF module 212then steps up the outgoing signal to the radio frequency prior to thetransmission of the signal by the antenna 110. Alternatively, the upconversion and down conversion can be performed in a single stage or inmore than two stages.

The base station 200 shown in FIG. 1 e includes two half-duplex modems106, two half-duplex ODU 108, and two antennas 110. The two half-duplexmodems 106, the two half-duplex ODU 108, and the two antennas 110operate as described with respect to nodes 402, 404.

The base station 200 is configured to communicate with nodes in multiplesectors. The base station components 211(a) communicate with node 402.Base station components 211(b) communicate with node 404. Similarly,node 402 communicates with base station components 211(a). Node 404communicates with the base station components 211(b). Thus, the basestation 200 communicates with both nodes 402, 404. For ease ofdescription, only one node is shown communicating with each base stationmodem in FIG. 1 e. However, multiple nodes can be present in any givensector to form a point to multi-point communication system with the basestation. With multiple nodes, the antenna 110 in FIG. 1 e transmits andreceives between the nodes in one sector of a coverage area. A differentantenna 110 may transmit and receive between the nodes in another sectorof a coverage area or in the same sector but another physical channel.

The nodes 402, 404 are synchronized such that only one node transmitsduring any given period of time. The nodes 402, 404 utilizes a timingsignal, for example a timing signal transmitted by the base station tothe nodes 402, 404, to maintain synchronization. Alternatively, a GPSsignal may be used. The base station is the only transmitter operatingin the downlink direction; hence it transmits without having tosynchronize with other base stations.

The systems shown herein can be implemented using the systems, includinghardware and software, as are described, for example, in U.S. Pat. No.6,016,311, issued Jan. 18, 2000, titled Adaptive Time Division DuplexingMethod and Apparatus for Dynamic Bandwidth Allocation Within a WirelessCommunication System; application Ser. No. 09/316,518, filed May 21,1999, titled Method and Apparatus for Allocating Bandwidth in a WirelessCommunication System; application Ser. No. 09/430,379, filed Oct. 22,1999, titled Method and Apparatus for Data Transportation andSynchronization Between Mac and Physical Layers in a WirelessCommunication System; application Ser. No. 09/365,917, filed Aug. 3,1999, titled Frame Structure of an Adaptive Modulation WirelessCommunication System; application Ser. No. 09/471,295, filed Dec. 24,1999, titled Method and Apparatus for Concatenated Channel Coding in aData Transmission System; application Ser. No. 09/564,377, filed May 1,2000, titled Method and Apparatus for Concatenated Channel Coding withVariable Code Rate and Coding Gain in a Data Transmission System; andapplication Ser. No. 09/539,851, filed Mar. 31, 2000, titled Method andApparatus for Reducing Co-Channel Interference in a Frame-SynchronizedWireless Communication System the disclosures of which are herebyincorporated by reference. Such an implementation would require theaddition of an offset to the millimeter-wave transceiver within theoutdoor unit. The outdoor unit and the indoor unit sections would remainhalf-duplex as disclosed in the above incorporated patents andapplications.

FIG. 1 f is a block diagram of a frame structure that includes twophysical channels. The frame structure can be used with thecommunication system of FIG. 1 e. The Figure represents a discrete timesegment. Physical channel A 301 is allocated for downlinks from the basestation components 211(a), 211(b) to the first and second nodes 402, 404(See FIG. 1 e). The base station alternates its broadcast between asubframe 140 which includes information for node 402 and a subframe 142which includes information for node 404.

Physical channel B 302 is allocated for subframes 420, 422 in an uplinkdirection from the first and second nodes 402, 404 to the base station200. Node 404 transmit information to the base station components 211(b)(See FIG. 1 e) during subframe 420. Node 402 transmit information to thebase station components 211(a) (See FIG. 1 e) during subframe 422. Node402 and node 404 can alternate in their transmission of subframes 420,422 on physical channel B 302. Thus, the base station 200 receivesalternating subframes from the nodes 402, 404 on physical channel B 302.Alternatively, the assigning of subframes of physical channel B can bevaried depending, for example, on the bandwidth requirements of thenodes. The term channel is used to mean a band or range of frequenciesof sufficient width for communication, e.g., 26.500 GHz to 26.525 GHz (a25 MHz wide channel).

Physical channel A 301 includes the downlinks from base stationcomponents 211(a) to node 402 while physical channel B 302 includes theuplinks from node 402 to base station components 211(a). Thus, subframes140 and 422 from physical channels A and B, respectively, form a logicalchannel between node 402 and base station components 211(a). Similarly,physical channel A 301 includes the downlinks from base stationcomponents 211(b) to node 404 while physical channel B 302 includes theuplinks from node 404 to base station components 211(b). Thus, subframes142 and 420 from physical channels A and B, respectively, also form alogical channel between node 404 and base station components 211(b). Forexample, the uplink and downlink subframes that form the logical channelbetween node 402(a) and the base station components 211(a) areillustrated by frame 113. In contrast to the FDD system illustrated inFIGS. 1 c and 1 d which uses two physical channels to produce a singlelogical channel, the system 300 illustrated in FIGS. 1 e and 1 fproduces two logical channels with the same number of physical channels.

Referring to FIGS 1 e and 1 f, each RF module 210 of each node isconfigured to allow its node to utilize both available physical channels301, 302. For example, when node 404 transmits information to basestation 200, its RF module 210 selects channel 302 for the information'stransmission through its antenna 110. When node 404 is scheduled toreceive information from the base station 200, its RF module 210switches from channel 302 to channel 301. Thus, node 404 uses bothchannels 301, 302.

Both nodes 402, 404 and the base station 200 may perform the tasksascribed to them using a combination of hardware, firmware and softwarecontrol. Engineering considerations drive the allocation of functions tosoftware, firmware and/or hardware. In particular, both nodes 402, 404and the base station 200 will generally employ a computer running asoftware program which perform the ascribed functions, or directshardware to performs the ascribed tasks in functional modules preparedfor such tasks. At least some of the physical communication is performedin hardware, but data manipulations may be performed, for example, by acomputer operating under software control, or by microprocessorsoperating under firmware control, or by application specific integratedcircuits (ASICs) or field programmable gate array, a portion of which isused for the specific manipulations.

FIG. 1 g is a block diagram of a first node 402 and a second node 404communicating with a full-duplex base station 406 in an FDDcommunication region. The system 400 provides wireless connectivitybetween the base station 406 and the first and second nodes 402, 404.

Each node 402, 404 can include a half-duplex modem 106, a half-duplexoutdoor unit (“ODU”) 108, and an antenna 110, for example a directionalantenna. The modem 106, ODU 108, and antenna 110 are the same asdescribed with reference to FIG. 1 e.

The base station 406 shown in FIG. 1 g includes a full-duplex modem 408,a full-duplex ODU 410, and a full-duplex antenna 412, for example, asmart antenna. The base station 406 transmits an outgoing signal andreceives an incoming signal simultaneously on different channels. Thefull-duplex modem 408 is configured to modulate and demodulate anincoming signal and to demodulate an outgoing signal simultaneously. Thefull-duplex ODU down converts the incoming signal from a radio frequencyin stages to a base band frequency. The full-duplex ODU also upconvertsa modulated base band signal in stages prior to transmission of theoutgoing signal at the radio frequency. Alternatively, the up conversionand down conversion can occur in one stage or more than two stages.

The full-duplex ODU 410 can include a full-duplex intermediate frequency(“IF”) module 409 and a full-duplex radio frequency (“RF”) module 411.The full-duplex IF module 409 is configured to simultaneously upconvertan outgoing signal and down convert an incoming signal on differentchannels. The full-duplex RF module 411 is configured to simultaneouslyupconvert the outgoing signal from the IF module and down convert anincoming signal from the antenna 412. The antenna 412 is configured tosimultaneously transmit to a first sector and receives from a secondsector within a coverage area. For example, the antenna 412 transmits totwo independent sectors simultaneously.

Alternatively, the base station can include two half-duplex modems 106and a hybrid ODU. The hybrid ODU includes two half-duplex IF modules 212and a full-duplex RF module 411. The full-duplex RF module permitssimultaneous reception and transmission of subframes of information bythe base station. The RF module is tuned to both transmit and receive onboth physical channels, however, the two half-duplex IF modules aretuned to the same channel. This alternative is more fully described withreference to FIG. 9 below.

The nodes 402, 404 are synchronized such that only one node transmitsduring any given period of time. The nodes 402, 404 utilizes a timingsignal, for example a timing signal transmitted by the base station tothe nodes 402, 404, to maintain synchronization. Alternatively, thenodes may use a GPS signal. The base station 406 is the only transmitteroperating in the downlink direction; hence it transmits without havingto synchronize with other base stations. Although, as will be describedlater with respect to FIG. 10, synchronization with other base stationscan be desirable to reduce co-channel interference.

FIG. 2 is a block diagram of a frame structure which can be used withthe communication system of FIG. 1 g. The Figure represents a discretetime segment. For example, physical channel A 301 is allocated for thedownlink from the base station 406 to the first and second nodes 402,404 (See FIG. 1 g). The base station 406 alternates its broadcastbetween a subframe 416 which includes information for node 402 and asubframe 418 which includes information for node 404.

Physical channel B 302 is allocated for subframes 420, 422 in an uplinkdirection from the first and second nodes 402, 404 to the base station406. Node 402 and node 404 can alternate in their transmission ofsubframes 420, 422. Subframe 420 includes information transmitted bynode 404 while subframe 422 includes information transmitted by node402. Thus, the base station 406 receives alternating subframes from thenodes 402, 404 on physical channel 302. Alternatively, the assigning ofsubframes on physical channel B can be varied depending, for example, onthe bandwidth requirements of the nodes.

Physical channel A 301 includes the downlinks from base station 406 tonode 404 while physical channel B 302 includes the uplinks from node 404to base station 406. Thus, subframes 418 and 420 from physical channelsA and B, respectively, form a logical channel between node 404 and basestation 406. Similarly, physical channel A 301 includes the downlinksfrom base station 406 to node 402 while physical channel B 302 includesthe uplinks from node 402 to base station 406. Thus, subframes 416 and422 from physical channels A and B, respectively, also form a logicalchannel between node 402 and base station 406. For example, the uplinkand downlink subframes that form the logical channel between node 402and the base station are illustrated by frame 114.

Referring to FIGS 1 g and 2, each RF module 210 of each node isconfigured to allow its node to utilize both available physical channels301, 302. For example, when node 404 transmits information, its RFmodule 210 selects channel 302 for the information's transmissionthrough its antenna 110. When node 404 is scheduled to receiveinformation from base station 406, its RF module 210 switches fromchannel 302 to channel 301. Thus, node 404 uses both channels 301, 302.

FIG. 3 is a block diagram showing the signal paths through nodes 402 andnodes 404. The described signal path also illustrates the signal paththrough the base station components 211(a), 211(b) (See FIG. 1 e). Forease of description, the signal path will be described with reference tonode 402. Although the following discussion relates to a system thattransmits information within the Local Multi-Point Distribution Services(LMDS) band at frequencies of approximately 28 GHz, the system is not solimited. Embodiments of the system are designed to transmit informationat frequencies, for example, of 10 GHz to 66 GHz.

As shown in FIG. 3, a signal is received on a radio frequency (“RF”) atthe antenna 110. The signal is passed into an RF module 210 for downconversion to an intermediate frequency (“IF”). The RF module 210 caninclude a duplexer 250, an RF down conversion module 252, an upconversion module 254, and a millimeter-wave band frequency synthesizer256. The duplexer 250 is configured to switch between a receive channel302, channel B and a transmit channel 301, channel A (See FIG. 2).Alternatively, the duplexer 250 can be configured to simultaneouslytransmit and receive to eliminate having the duplexer 250 switch betweenthe receive and transmit channels. Data received on channel A follows areceive signal path 258. Conversely, data transmitted by nodes 402, 404on channel B follows a transmit signal path 260.

Within the RF module 210, the received signal from the antenna 110 issent to an RF down conversion module 252 for down conversion to anintermediate frequency (“IF”). The RF down conversion module 252communicates with the millimeter-wave band frequency synthesizer 256 todown convert the received signal to the IF. The millimeter-wave bandfrequency synthesizer 256 maintains a fixed offset 262 between the bandof frequencies assigned to channel B and the band of frequenciesassigned to channel A. The frequency offset 262 is selected based on thefrequency separation between channel A and channel B.

Continuing along the receive signal path 258, the received signal passesto the IF module 212 via switch 270. If the switch 270 is set to receivemode, the received signal is sent to the IF module 212. The IF module212 includes an IF down conversion module 262, an IF up conversionmodule 264, and an IF band synthesizer 266. The IF down conversionmodule 262 uses the IF band synthesizer 266 to further down convert thereceived signal to a base band signal prior to its transmission to themodem 106 via switch 268. If the switch 268 is set to receive mode, thereceived signal passes to the modem 106.

Turning to the transmit signal path 260, once data is modulated by themodem 106 into a transmit signal, it is fed to the IF module 212 throughthe switch 268. If the switch 268 is set to transmit mode, the transmitsignal is sent to the IF up conversion module 264. The IF up conversionmodule 264 up converts the base band signal to an IF through the IF bandsynthesizer 266. Once the transmit signal has been up-converted to theIF, it continues along the transmit signal path 260 to the RF module 210through the switch 270. If the switch 270 is set to transmit mode, thetransmit signal is sent to the RF up conversion module 254.

The RF up conversion module 254 includes the millimeter-wave bandfrequency synthesizer 256 for up-converting the transmit signal to theradio frequency of, for example, approximately 28 GHz (LMDS band). Asmentioned above, the millimeter-wave band frequency synthesizer 256applies the frequency offset 262 to the transmit signal. The frequencyoffset 262 is selected based on the frequency separation between channelA and channel B. Once the transmit signal is offset from the receivedsignal, the signal passes through the duplexer 250 and is transmittedover the air through the antenna 110 to the base station 406.

FIG. 4 is a block diagram of nodes 502(a), 502(b) in a first sector andnodes 504(a), 504(b) in a second sector communicating with a basestation 200 in an FDD communication region. The first and second sectorsare located within the coverage area of the base station 200. Additionalnodes can be included depending on system requirements. Only four nodesare shown for ease of description. Each node includes a modem 106, anODU 108, and an antenna 110 all as described with reference to FIG. 1 e.The base station 200 can include base station components 211(a), 211(b)along with their respective antennas 110, all as described withreference to FIG. 1 e.

FIG. 5 is a block diagram of a frame structure that includes twophysical channels for use with the communication system of FIG. 4.Referring now to FIGS. 4 and 5, the base station 200 transmits to nodes504(a), 504(b) in a subframe and to nodes 502(a), 502 (b) in a differentsubframe all on the downlink physical channel A 301. For example, duringsubframe 510 the base station components 211(b) transmit informationintended for nodes 502(a), 502(b). During subframe 512 the base station200 transmits information intended for nodes 504(a), 504(b). Each groupof nodes 502, 504 alternates in its transmission of frames to the basestation on an uplink physical channel B 302. For example, during asubframe 514 nodes 504(a)-(b) transmit information that is intended forthe base station components 211(a). Following subframe 514 is a subframe516 during which nodes 502(a)-(b) transmit information to the basestation components 211(b). However, both the length of the subframe ofthe channels can be varied or fixed and similarly, the patterns oftransmission and reception can be varied.

FIG. 6 illustrates an example of a downlink subframe 600, for example,subframe 510 for use by the base station 200 in transmitting informationto nodes 504(a), 504(b) on the downlink physical channel A of FIG. 5.The downlink subframe 600 also represents the subframe 512 which is usedby the base station 200 to transmit information to nodes 502(a), 502(b)on the downlink channel A of FIG. 5. For ease of description, thedownlink subframe 510 used by the base station components 211(b) willonly be described. The frame 600 is subdivided into a plurality ofphysical layer slots (PS) 602. The subframe 600 can be, for example,one-half millisecond in duration and include 400 physical slots.Alternatively, subframes having longer or shorter duration and with moreor fewer PSs can be used.

Each downlink subframe 600 can include a frame control header 604 anddownlink data 606. The frame control header 604 includes information forsynchronizing with the nodes 502. The base station 406 maintains adownlink subframe map that reflects the downlink PS 602 allocation. Theframe control header 604 can include a map of one or more subsequentuplink subframes that are to be transmitted by the pluralities of nodes.For example, referring to FIG. 5 frame 510 can include the map for thesubsequent uplink subframe 516. Turning back to FIG. 6, the framecontrol header 604 can further include a map of attributes of thedownlink data 606. For example, attributes may include, but are notlimited to, the locations of the PSs in the frame that are intended foreach individual node.

The downlink data 606 is transmitted in a pre-defined modulation or asequence of modulation techniques Mod-A, Mod-B, Mod-C. For example, asequence such as: QAM-4, followed by QAM-16, followed by QAM-64 could beused. Each node can monitor the information in the subframe 510 andretains only those messages intended for it. Attributes in the framecontrol header 604 provide this information to the nodes.

FIG. 7 illustrates an example of two uplink subframes 514, 516. Duringsubframe 514 nodes 504 (see FIG. 5) transmit information to the basestation. In this example, during subframe 516 nodes 502 (see FIG. 5)transmit information to the base station. Each uplink subframe 514, 516comprises uplink data 702. The subframes 514, 516 are subdivided into aplurality of physical layer slots (PS) 602.

Each node transmits its information during its allocated PS 602 or rangeof PSs 602. The PSs 602 allocated for each node are grouped into acontiguous block of a group of data blocks 704(a)-(n). When uplinksubframe 514 is transmitted, nodes 504(a)-(n) use data blocks704(a)-(n). Similarly, when uplink subframe 516 is transmitted, nodes502(a)-(n) use data blocks 704(a)-(n). The range of PSs 602 allocated toeach data block 704(a)-(n) is determined by the base station.

The data transmitted in each data block 704(a)-(n) is modulated by thetransmitting node. During its data block, the node transmits with afixed modulation that can be selected based on the effects ofenvironmental factors on the transmission between that node and the basestation. Alternatively, a sequence of modulation techniques can be usedin each data block 704(a)-(n) or the data blocks 704(a)-(n) can begrouped by modulation type.

FIG. 8 illustrates an example of a transmission sequence of an uplinksubframe map in the downlink subframe 510, 512 (see FIG. 5). As shown byarrow 800(a), the frame control header 604, which is part of frame 510,includes a map of the PSs 602 in the subsequent uplink subframe 516.Similarly, the frame control header 604, which is part of downlinksubframe 512, includes a map of the PSs 602 in the subsequent uplinksubframe 514 as shown by arrow 800(b). The attributes of the downlinksubframe 510 can be included in its frame control header 604 asillustrated by arrow 802(a). Similarly, the attributes of the downlinkframe 512 can be included in its frame control header 604 as illustratedby arrow 802(b).

FIG. 9 is a block diagram of a base station 901 which includes a hybridODU 900 and two half-duplex modems 106. The hybrid ODU 900 includes afull-duplex RF module 902 and two half-duplex IF modules 212. The RFmodule 902 is shared by both modems 106. The full-duplex RF module 902includes a transmitter module 904 and a receiver module 906 configuredto transmit and receive outgoing and incoming signals, respectively. Forexample, when one of the two modems 106 is transmitting, that modemutilizes the transmitter module 904. The RF module 902 is configuredsuch that the transmitter module 904 transmits during a time frame on afirst channel while the receiver module 906 simultaneously receives on asecond channel. Thus, during the same time frame the receiver module isavailable for receiving an incoming signal destined for the second ofthe two modems. The two modems are synchronized so as to alternate intheir shared use of the RF module 902.

FIG. 10 is a diagram showing uplink channels A and B being used fourtimes in a cell by half-duplex nodes. Each base station 1001(a)-(d)includes four sets of base station components 211(a)-(d) and fourantenna 110 (See FIG. 5). Each of the four sets of base stationcomponents is configured to communicate with the half-duplex nodes in adifferent sector. Each base station 1001(a)-(d) communicates with agroup of nodes in the base station's coverage area, or cell. Clusters offour sectors 1002(a)-(d) surround each base station 1001(a)-(d). Eachcluster of four sectors forms a cell 1004(a)-(d). The cells are shown asseparated by bold lines 1006, 1008. Each cell 1002(a)-(d) comprises fouror six sectors. In the case of a four sector cell, the coverage areacovered by the sector is square (as shown in FIG. 10). In the case ofsix sectors, the coverage area covered by the cell is hexagonal.

Each cell 1004 has an associated and corresponding base stationcomponents 211(a)-(d). For example, cell 1004(a) has a correspondingbase station 1001(a). Each set of base station components 211(a)-(d) hasan antenna 110 for communicating with the nodes within its associatedsector 1002(a)-(d). Thus, the base station 1001 includes four sectoredantenna, one for communicating with each sector 1002(a)-(d). Each sectorcontains a group of nodes that communicate with the base station 1001 ona unique logical channel at any given time.

In accordance with frequency re-use methodologies and techniques, a setof two physical channels is allocated for use in each cell 1004(a)-(d).Physical channel A is allocated for downlink transmissions throughoutthe cell. Physical channel B is allocated for uplink transmissionsthroughout the cell. As shown in FIG. 10, for example, each cell 1004utilizes a set of four orthogonal physical channels (A, A′, B, B′)comprising the two physical channels (A and B) for uplink and downlinkcommunications between the nodes and the base station. Physical channelsA and B each have two different polarizations (designated by the primeand non-prime indicators). As explained with reference to FIGS 1 e and 1f, each pair of physical channels forms two logical channels. Since fourorthogonal channels are available for use in FIG. 10, four logicalchannels are formed. Each logical channel includes alternating subframesfrom two of the four available physical channels (A, A′, B, B′). Sincephysical channels A and A′ are used for downlinks within each cell, eachlogical channel will include either A or A′. Since physical channels Band B′ are used for uplinks within each cell, each logical channel willinclude either B or B′. Each sector 1002(a)-(d) of a cell 1004(a)-(d)therefore utilizes a different logical channel for communication betweenthe nodes in the sector 1002 and the associated base station 1001. Ineach cell 1004(a)-(d), the pattern of frequency distribution is a mirrorimage of the adjacent and diagonal cells 1004(a)-(d). Thus, for example,sector 1002(a) of cell 1004(a) uses the same logical channel as sector1002(b) of cell 1004(b).

The nodes within two adjacent sectors, for example, sectors 1002(a),1002(b), are synchronized such that only nodes in one of the two sectorstransmits during any given period of time. As shown in FIG. 10, sector1002(a) receives its downlink from the base station on physical channelA′ while sector 1002(b) transmits its uplink to the base station onphysical channel B′. Since both of these occur during paralleltimeframes of channels A′ and B′, they are both illustrated as even inFIG. 10. During the same period of time, nodes within sector 1002(c) areuplinking to the base station on physical channel B. During the sametime period, nodes within sector 1002(d) are downlinking to the basestation on physical channel A. The nodes can utilizes a timing signal,for example a timing signal may be transmitted by the base station tothe nodes, to maintain synchronization. Alternatively, the nodes may usea GPS signal.

Still referring to FIG. 10, each node in the sectors utilizes an antenna110 (see FIG. 4) for communicating with its associated base station1001(a)-(d). Each node operates as described with reference to FIG. 1 gto utilize 50% of the channel capacity. The antenna 110 is pointedtowards the associated base station 1001(a)-(d). However, without anysystem wide synchronization between base stations, each base stationreceives energy from any node operating on the same RF channel and ispositioned on a line of site (LoS) relative to the sectored antenna ofthe base station. The use of system wide synchronization to minimizeco-channel interference will be discussed with respect to FIGS. 11 and12.

FIG. 11 illustrates four adjacent sectors from four different cellswhere co-channel interference occurs due to uncorrelated rain fades. Anexample of such a configuration is shown at the center of FIG. 10.Returning to FIG. 11, base stations 1001(a)-(d) are located in sectors1002(d), 1002(c), 1306, 1308, respectively. Each of the four sectors liewithin a different cell wherein frequency re-use is employed (i.e. twochannels are used four times within a cell). The four sectors usephysical channel A for downlinks to their associated base stations andphysical channel B for uplinks to their associated base stations.

Node 402 and its antenna 110 (see FIG. 1 g) are located near bold line1006 and transmit along the line of sight (“LoS”) towards base station1001(c). While the antenna 110 transmits information along the LoStowards base station 1001(d), unwanted noise is also transmitted along aside lobe path 1318 at an angle 1320. As the angle 1320 is increasedaway from the LoS, the strength of the unwanted noise transmitted by theantenna 110 decreases. For example, when the angle reaches 63 degreesthe signal strength along lobe path 1318 is at least 30 dB less than thesignal strength along the LoS.

Under typical environmental conditions, i.e. wind, snow, and smog, thenode 402 transmits along the LoS at a nominal power level. Under theseconditions, the 30 dB decrease minimizes the potential for co-channelinterference occurring with base station 1001(d). However, under adverseenvironmental conditions, i.e. rain, the node 402 increases itstransmitting power level to counteract signal fade so that its signalreaches base station 1001(c). If the side lobe path 1318 is alsoexperiencing adverse environmental conditions, this increase intransmission power level does not substantially increase the potentialfor co-channel interference with base station 1001(d). However, if theside lobe path 1318 is not experiencing similar adverse conditions, thenode's increase in transmission power towards base station 1001(c) willincrease the potential for co-channel interference with base station1001(d).

FIG. 12 shows the four sectors from FIG. 11 configured to use differenttime offsets of physical channels A and B to reduce co-channelinterference caused by the adverse weather scenario of FIG. 11. In FIG.12, base stations 1001(c), 1001(d) receive and transmit information withtheir associated nodes during different time offsets or subframes.Similarly, adjacent base stations 1001(a), 1001(b) receive informationfrom their associated nodes during different time offsets or subframes.For example, when an uplink on channel B along a side load path 1318reaches base station 1001(d), the base station 1001(d) is in atransmission mode, not a receiving mode. For example, base station1001(d) is transmitting a downlink to nodes in sector 1308 on channel A.By using different time offsets for sectors 1002(c), 1308 as compared tosectors 1002(c), 1306, the potential for co-channel interference betweenadjacent sectors is reduced under adverse weather conditions.

Aspects of the present invention have been disclosed in one or moreexemplary embodiments. These embodiments are not to be construed aslimiting, but rather as showing a way to practice the invention. Thescope of the invention is defined by the claims which follow.

1. A method for communicating between half-duplex nodes and a basestation, where at least one half-duplex node is to transmit on an uplinkchannel and receive on a downlink channel in a frequency divisionduplexing (“FDD”) manner, the method comprising: transmitting modulateddata from the base station to a first half-duplex node during a firsttime frame on a first channel; receiving modulated data from a secondhalf-duplex node at the base station during the first time frame on asecond channel, the first and second half-duplex nodes being differentnodes, and the transmitting and the receiving in the first time frameoccurring substantially simultaneously; transmitting modulated data fromthe base station to the second half-duplex node during a second timeframe on the first channel, wherein the first time frame precedes thesecond time frame; and receiving modulated data from the firsthalf-duplex node at the base station during the second time frame on thesecond channel, the transmitting and the receiving in the second timeframe occurring substantially simultaneously.
 2. The method of claim 1,wherein said transmitting modulated data to the first half-duplex nodeis performed by a first half-duplex modem and said transmittingmodulated data to the second half-duplex node is performed by a secondhalf-duplex modem, wherein the base station includes the first andsecond half-duplex modems.
 3. The method of claim 2, wherein themodulated data transmitted by the first half-duplex node is received bythe first half-duplex modem and wherein the modulated data transmittedby the second half-duplex node is received by the second half-duplexmodern.
 4. The method of claim 3, further comprising: transmittingmodulated data from a third half-duplex modem to a third half-duplexnode during the first time frame on a third channel; receiving modulateddata from a fourth half-duplex node at a fourth half-duplex modem duringthe first time frame on a fourth channel; transmitting modulated datafrom the fourth half-duplex modem to the fourth half-duplex node duringthe second time frame on the third channel; and receiving modulated datafrom the third half duplex node at the third half-duplex modem duringthe second time frame on the fourth channel.
 5. The method of claim 4,wherein the first channel and the third channel span a similar frequencyband but have different polarizations.
 6. The method of claim 5, whereinthe second channel and the fourth channel span a similar frequency bandbut have different polarizations.
 7. The method of claim 4, furthercomprising forming a first logical channel between the first half-duplexmodem and the first half-duplex node from the first and second channelsand forming a second logical channel between the second half-duplexmodem and the second half-duplex node from the first and secondchannels.
 8. The method of claim 7, further comprising forming a thirdlogical channel between the third half-duplex modem and the thirdhalf-duplex node from the third and fourth channels and forming a fourthlogical channel between the fourth half-duplex modem and the fourthhalf-duplex node from the first and second channels.
 9. The method ofclaim 2, wherein the first half-duplex modem and the second half-duplexmodem are connected to a full-duplex outdoor unit, the full-duplexoutdoor unit to substantially simultaneously communicate with the firsthalf-duplex node and the second half-duplex node.
 10. The method ofclaim 1, further comprising adapting the first half-duplex node tooperate in a first frequency division half-duplex manner and adaptingthe second half-duplex node to operate in a frequency divisionhalf-duplex manner.
 11. The method of claim 1, further comprisingadapting the base station to communicate with the first half-duplex nodeand the second half-duplex node in a frequency division half-duplexmanner.
 12. The method of claim 1, wherein transmitting modulated datato the first half-duplex node and transmitting modulated data to thesecond half-duplex node is performed by a full-duplex modem.
 13. Themethod of claim 12, wherein the full-duplex modem is connected to afull-duplex outdoor unit, the full-duplex outdoor unit to substantiallysimultaneously communicate with the first half-duplex node and thesecond half-duplex node.
 14. A wireless communication system to transmitand receive information between half-duplex nodes and half-duplex basestations in a frequency division duplexing (“FDD”) manner, the systemcomprising: a first half-duplex node to transmit modulated data over afirst channel and to receive modulated data over a second channel; asecond half-duplex node, remotely disposed from the first-duplex node,to transmit modulated data over the first channel and to receivemodulated data over the second channel such that the first and secondhalf-duplex nodes are synchronized to transmit while the other isreceiving and receive while the other is transmitting; a firsthalf-duplex base station to transmit modulated data to the firsthalf-duplex node over the second channel and to receive modulated datafrom the first half-duplex node over the first channel; and a secondhalf-duplex base station, remotely disposed from the first half-duplexbase station, configured to transmit modulated data to the secondhalf-duplex node over the second channel and to receive modulated datafrom the first half-duplex node over the first channel.
 15. The systemof claim 14, wherein the first half-duplex node and the secondhalf-duplex node are synchronized by timing signals received form thefirst and second half-duplex base stations.
 16. The system of the claim14, wherein the first and second half-duplex base stations aresynchronized using a wired line.
 17. A method for communicating betweenhalf-duplex nodes and half-duplex base stations, wherein at least one ofsaid half-duplex nodes is to transmit on an uplink channel and receiveon a downlink channel in a frequency division duplexing (“FDD”) manner,the method comprising; downlinking modulated data from a base station bya first half-duplex node during a first time frame on a first channel;uplinking modulated data from the base station by a second half-duplexnode during the first time frame on a second channel, the first andsecond half-duplex nodes being different nodes downlinking and theuplinking in the first time frame occurring substantiallysimultaneously; downlinking modulated data during a second time frame onthe first channel, wherein the first time frame precedes the second timeframe; and uplinking modulated data during the second time frame on thesecond channel the downlinking and the uplinking in the second timeframe occurring substantially simultaneously.
 18. A method forcommunicating between half-duplex nodes and a base station, at least oneof said half-duplex nodes is to transmit on an uplink channel andreceive on a downlink channel in a frequency division duplexing (“FDD”)manner to reduce co-channel interference, the method comprising:transmitting modulated data from a base station to a first half-duplexnode during a first time frame on a first channel; receiving modulateddata from a second half-duplex node at the base station during the firsttime frame on a second channel, the first and second half-duplex nodesbeing different nodes, and the transmitting and the receiving in thefirst time frame occurring substantially simultaneously; transmittingmodulated data from the base station to the second half-duplex nodeduring a second time frame on the first channel, wherein the first timeframe precedes the second time frame; and receiving modulated data fromthe first half-duplex node at the base station during the second timeframe on the second channel, the transmitting and the receiving in thesecond time frame occurring substantially simultaneously.
 19. The methodof claim 18, wherein transmitting modulated data to the firsthalf-duplex node is performed by a first half-duplex modem andtransmitting modulated data to the second half-duplex node is performedby a second half-duplex modem, wherein the first and second half-duplexmodems are located at the base station.
 20. The method of claim 19,wherein the modulated data from the first half-duplex node is receivedby the first half-duplex modem and wherein the modulated data from thesecond half-duplex node is received by the second half-duplex modem. 21.The method of claim 20, further comprising: transmitting modulated datafrom a third half-duplex modem to a third half-duplex node during thefirst time frame on a third channel; receiving data from a fourthhalf-duplex node at a fourth half-duplex modem during the first timeframe on a fourth channel; transmitting modulated data from the fourthhalf-duplex modern to the fourth half duplex node during the second timeframe on the third channel; and receiving modulated data from the thirdhalf-duplex node at the third half-duplex modem during the second timeframe on the fourth channel.
 22. The method of claim 21, wherein thefirst channel and the third channel span a similar frequency band buthave different polarizations.
 23. The method of claim 22, wherein thesecond channel and the fourth channel span a similar frequency band buthave different polarizations.
 24. The method of claim 21, wherein thefirst half-duplex modem, the second half-duplex modem, the thirdhalf-duplex modern, and the fourth half-duplex modem are co-located atthe base station.
 25. The method of claim 21, wherein the third andfourth channels form a third logical channel between the thirdhalf-duplex modern and the third half-duplex node and also form a fourthlogical channel between the fourth half-duplex modem and the fourthhalf-duplex node.
 26. The method of claim 18, further comprisingconnecting the first half-duplex modem and the second half-duplex modernto a full-duplex outdoor unit, the full-duplex outdoor unit tosubstantially simultaneously communicate with the first half-duplex nodeand the second half-duplex node.